Control of regeneration in signaling systems



Sept. 10, 1929. I s, OHL 1,727,408

CONTROL OI" REGENERATION IN SIGNALING SYSTEIS' Fil'ed Feb. 20, 1926INVENTOR A TTORNE Y Patented Sept. 10, 1929.

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RUSSELL S. OHL, OF NEW YORK, N. Y., ASSIGNOB TO AMERICAN TELEPHONE 'ANDTELEGRAPH COIIIPANY, A CORPORATION 9F NEW' Application filed February20, 1926. Serial No. 89,795;

This invention relates to signaling systems, and particularly toarrangements in regenerative systems for controlling the magnitude ofregeneration.

In a vacuum tube having an input circuit and an output circuit which arecoupled so as to feed energy in the output circuit back to the inputcircuit, when the coupling is varied so as to control the rate at whichenergy in the output circuit is fed back to the input circuit,thefrequency at which the input circuit is tuned is changed. In order totune the input circuit to the same frequency that it previously had, itis necessary to make two adjustments, onedetermining the frequency ofthe input circuit and the other determining the magnitude ofregeneration. The fact that two adjustments are necessary, one involvinga change in the frequency of the circuit to control the magnitude ofregeneration in a vacuum tube having coupled input and output circuits,makes the system highly undesirable, especially where high frequenciesare concerned.

It is an object of the invention to control regeneration in a vacuumtube having an input circuit and an output circuit having a fixedcoupling therebetween by impressing another frequency on the inputcircuit and varying the amplitude of this other frequency to controlregeneration.

It is another object of this invention to re ceive signals which aremodulated on a carrier Wave impressed on a vacuum tube set up forregeneration by impressing another wave of constant frequency on thevacuum tube and controlling the regeneration by varying the amplitude ofthis other wave.

While the nature of the invention will be pointed out with particularityin the appended claims, the invention itself, both as to its objects andfeatures, will be better understood from the detailed descriptionhereinafter following when read in connection with the accompanyingdrawing showing two embodiments of the invention relating to the controlof regeneration in vacuum tubes.

Referring to Figure 1, there is shown a radio receiving system forreceiving signals modulated on a carrier wave impressed on the system.There are three three-element vacuum tubes which are set up as theoscile lator O, the amplifier A and the detector D, respectively. Theoscillator O is. of thetuned grid type having a tuned grid circuitcomprising an inductance 11 and acondenser 12, the inductance 11 Whichisbetween the grid and cathode of the oscillator O bemg inductivelycoupled to the inductance 13 which is between the anode and a batterylet. The inductance .11 and condenser 12 together form a tuned circuithaving negligible reactance the frequency of the oscillator. Thebattery14 is employed for supplying the potential for the anode of theoscillator O.- it will be understood, however, that the oscillator 0 maybe of any type well known in the art, preferably any vacuum tubeoscillator sustaining oscillations of an inaudible frequency; i I.

An amplifier A is coupled to the oscillator 0 through a potentiometer 15having a movable arm 16 associated therewith for con trolling thepotential and, consequently the amplitude of the voltage of theoscillator O, impressed between the grid and cathode of the amplifier A.A battery 17 is employed for supplying the necessary potential to theanode of the amplifier A through the primary winding of a transformerT.It will be understood, however, that the amplifier A may be of anywell-known type, preferably any vacuum tube amplifier. A condenser 18 isbridged across the secondary winding of the transformer T, the secondaryWinding of the transformer T and the condenser 18together forming acircuit tuned to the frequency of the oscillator 0 having negligiblereactance at the frequency of the oscillator O. A three-element vacuumtube D having an anode, a cathode and a grid is set up so that an inputcircuit is connected between its grid; and cathode including aninductance 19 and an output circuit is connected between its anode andcathode including aninductance 20. These inductances, 19 and 20, are soarranged that energy in the output circuit is fed back to the inputcircuit, the coupling between these inductances being fixed. A receivingcircuit connected to a receiving Cir antenna'RA is also coupled to theinductances 19 and 20 through an inductance 21 included in the receivingcircuit. The variable condenser 22 tunes the circuit which includes thesecondary winding of the transformer T, the condenser 18, the inductance19 and the condenser 22 to a frequency different from the frequency towhich the secondary winding of the transformer T and the condenser 18are tuned. A battery 23 supplies the potential for the'anode of thedetector D through a telephone receiver 24: and the inductance 20. Thetelephone receiver 2-1 receives the signals. after detection by thedetector D, a condenser 25 bridging the telephone receiver 24? forforming apath of low impedance to high frequency waves.

"In this invention the oscillator O sustains oscillationsof a definitefrequency which is used to control the effective resistance in the inputcircuitof the detector D as well as the magnitude of regeneration in thesystem. The particular frequency of the oscillations sustained byoscillator O is immaterial. However, as the amplitude of theseoscillations increases, the effective resistance in the input circuit ofdetector D increases and vice versa.

A fixed .coupling exists between inductances 19, 20 and 21 which is ofthe inductive type. It will be understood, however, thatany other typeof coupling may be used equally Well to accomplish the same. end.Furthermore, the potential between the grid and cathode of the detectorD is varied by themova'ble arm 16 associated with the potentiometer 1 5in order to control the degree of regeneration existing between theoutput circuit and the input circuit of the detector D, thepotentiometer 15 being employed for controlling the magnitude of thevoltage of the amplifier A impressed, through the various tunedcircuits, between the grid and cathode of the detector D. Thus bycutting more resistance out of the potentiometer 15, the potentialbetween the grid and cathode of the detector D will be decreased, andconsequently the degree of regeneration between theoutput and inputcircuits of the detector D will also be decreased. On the other hand, bycutting less resistanceout of the potentiometer 15, the potentialbetween the grid and cathode of the detector D will be increased, andconsequently the degree of regeneration between the output and inputcircuits of the detector D'will also be increased. Furtherfore, thecontrol of regeneration does not involve any change in the frequency ofthe tuned circuits associated with the detectorD or in the'frequency'ofthe oscillator O, but merely involves an adjustment of the amplitude'ofthe frequency of the oscillator-O.

I Fig. 2 represents another embodiment of the invention for controllingregeneration. An oscillator O is set up as described in the patent to R.V. Hartley, No. 1,356,7 63, dated October 26, 1920, having an inductance31 in its input circuit, an inductance 32 in its output circuit and acondenser 33 bridging inductances 31 and 32. The inductances 31 and 32and the condenser 33 together form a circuit tuned to the frequency ofthe oscillator. An amplifier A is coupled to the oscillator O throughacondenser 3e and a potentiometer 35, saidpotentiometer having a movablearm 36 associated therewith for controlling the amplitude of thefrequency of the oscillator O impressed on the amplifier A A detector 'Dis coupled to the amplifier A through a transformer T,, the frequency ofthe oscillator periodically controlling the negative potential of thegrid with respect to the cathode.

The receiving circuit for receiving a high frequency wave modulated bysignals comprises the receiving antenna RA and an inductance 37 Theinductance 37 is coupled to inductances 38 and 39, the inductance 38being in the input circuit of the detector D and the inductance 39 beingin the output circuit of the detector D. The variable condenser 40 isemployed for tuning the circuit coupled to the inductance 37 whichincludes inductance 38, condenser all, inductance 39 and the variablecondenser 4.0. Choke coils 4:2 and 43 are connected in the input and output circuits of the detector D, respectively. A condenser 44 closes apath for high frequency waves in the output circuit of the detector D,which path includes the anode and cathode of the detector D, theinductance- 39 and the condenser ed.

Thetransformer T couples an amplifier A with the output circuit of thedetector D in order that the signals detected by the detector D may befurther amplified by the amplifier A telephone receiver 45 receives thesignals detected by the detector D and amplified by the amplifier A acondenser "I6 bridging the telephone receiver t5 and forming a path oflow impedance for high frequency currents.

A battery 47 supplies the potential for the anodes of the various vacuumtubes employed-in this system, the potential for the anode .of theoscillator 0 being supplied through a conductor 48 and the inductance32, the potential'for the anode of the amplifier A being suppliedthrough the conductor AS and the primary winding of the transformer Tthe potential for the anode of the detector D being supplied through theconductor .48, the primary winding of the transformer T the choke coil4&3 and the inductance 39, and the potential for the anode of theamplifier A being supplied through the telephone receiver 45.

The potential between the grid and cathode of the detector D iscontrolled by varying the amplitude of the wave transmitted by theoscillator O by means of the potentiometer 35 having the movable arm 36associated therewith. By virtue of the coupling between inductances 38and 39 in the input and output circuits of the detector D, respectively,the degree of regeneration is controlled by the potentiometer 35associated with the oscillator 0 While the invention has been shown anddescribed in two embodiments which have particular reference to systemsfor the reception of signals modulated on a high frequency wave, it isto be understood that the invention may be embodied in other and widelyvaried organizations and various other systems without departing fromthe spirit of the invention and the scope of the appended claims.

What is claimed is:

1. The method of controlling regeneration in a vacuum tube having aninput circuit and an output circuit with a XGCl coupling therebetween,which consists in impressing a wave of constant frequency on the inputcircuit of said vacuum tube and varying the amplitude of the impressedwave.

2. The method of receiving signals which consists in impressing acarrier wave modulated by signals on a three-element vacuum tube set upfor regeneration and controlling the regeneration by means of anotherwave of adjustable amplitude.

3. The method of receiving signals with a vacuum tube having an outputcircuit connected to its anode and cathode and an input circuitconnected to its grid and cathode, the energy in the output circuitbeing fed back to the input circuit due to a fixed coupling.thercbetween, which consists in impressing a high-frequency wavemodulated by signals and another wave of constant frequency on the inputcircuit, and adjusting the amplitude of said latter wave to control therate at which the energy is fed back from the output circuit to theinput circuit.

In a vacuum tube lniving an anode, a cathode and a grid in which aninductance is connected between the grid and the cathode and anotherinductance is connected between the anode and the cathode, saidinductances being coupled to each other for regeneration, the method ofreceiving signals which consists in impressing on the inductanceconnected between the grid and the cathode a wave modulated by signals,impressing another wave of constant frequency on the same inductance,and adjusting the amplitude of said latter wave to control the degree ofregeneration.

5. In a signal-receiving system, a vacuum tube having an anode, acathode and a grid, an input circuit connected to its grid and cathode,an output circuit connected to its anode and cathode, a fixed couplingexisting between said input circuit and said output circuit, anoscillator transmitting a wave of constant frequency which is impressedon said input circuit, and means forvarying the amplitudeof the latterwave for con trolling the regeneration.

6. A signal receivingsystem "comprising a three-element vacuumtubehaving an input circuit and an output circuit coupled together forregeneration, a wave modulated bysignals impressed onthe input circuitof said vacuum tube, another Wave of constant frequency also impressedon" the input circuit of said vacuum tube, and meansfor controlling thedegree of regcnerationfby varying the amplitude of said latter wave.

7. In a radio receivingsystem, incombination, a vacuum tube having ananode, a cathode and a grid, an input circuit connected to the grid andcathode, an output circuit connected to the anode and cathode, a fixedcoupling between the input circuit and the output circuit for feedingenerg in the output circuit back to the input circuit, a high-frequencywave modulated by signals impressed'on the input circuit, another waveof constant frequency also impressed on the input circuit, and means foradjusting the amplitudeof the latter wave to control the rate at whichenergy is fed from the output circuit back'to the input circuit.

SQA. radio receiving system comp using a vacuum tube having an anode, acathode and a grid, aninductance connected between the grid and thecathode, another inductance connected between the anode and the cathode,said inductances being coupled together for regeneration, a Wavemodulated by signals impressed on the inductance connected to the gridand the cathode, another wave of constant frequency also impressed onthe inductance connected to the grid and the cathode, and means foradjusting the amplitude of the latter wave to control the degree ofregeneration.

9. In a radio receiving system, an oscillator of constant frequency, athree-element vacuum tube having an anode, a cathode and a grid, areceiving circuit for receiving a high-frequency wave modulated by lowfrequency signals, three inductances, one inductance being connectedbetween the anode and the cathode of the three-electrode vacuum tube, asecond inductance being connected between the grid and the cathode ofthe three-electrode vacuum tube, and a third inductance being includedin the receiving circuit, said inductances bearing a fixed couplingtherebetween, an oscillator transmitting a wave which is impressed onthe inductance connected between the grid and the cathode of thethree-element vacuum tube, and a potentiometer, said potentiometer beingassociated With said oscillator for adjusting the amplitude of the avetransmitted thereby and controlling the magnitude of regeneration.

10. In a radio receiving system, an oscillator of constant frequency, anamplifier for amplifying oscillations of said oscillator, apotentiometer for controlling the gain of said amplifier, athree-element vacuum tube having an anode, a cathode and a grid, aninput circuit connected between the grid and the cathode of saidthree-element vacuum tube, an output circuit connected between the anodeand the cathode of said three-element vacuuin tube, and a receivingcircuit for receiving high-frequency oscillations modulated byloW-frequencysignals, said input circuit, said output circuit and saidreceiving circuit being invariably coupled together. i

11. In a signaling system, in combination, a high-frequency oscillator,a receiving circuit for receiving another high frequency modulated bysignals, a three-electrode vacuum tube having an input circuit includingthe grid and the cathode of said vacuum tube and an output circuitincluding the anode and the cathode of said vacuum tube, a pair ofinductances one in said input cir cuit and the other in said outputcircuit, said inductances having a fixed coupling therebetween forfeeding energy in said output circuit back into said input circuit, anda potentiometer for controlling the potential of the current transmittedby said highfrequency oscillator to the input circuit of said vacuumtube.

In testimony whereof, Ihave signed my name to this specification this18th day of February 1926.

- RUSSELL S. OHL.

